Piezoelectric (piezo) rotary motors have found their way into industrial applications where high torque, low rpm requirements are needed in small volumes. Magnetic flux motors are typically large, have a high rpm, and require gear reduction mechanisms to reduce speed. However, Shinsei Corporation produces 30 and 60 mm diameter piezoelectric or ultrasonic motors for testing and product applications. Other Japanese piezo motor manufacturers have incorporated 60 mm diameter motors in automobile seat and steering column adjustments while some have been used in window blind motorized mechanisms. These applications all require high torque, low speed outputs within a small volume.
Honeywell Federal Manufacturing and Technologies (H-FM&T), Kansas City, Mo., has developed and marketed a 17 mm diameter motor for military testing, evaluation, and applications. More recently, H-FM&T has developed jointly with Sandia National Laboratories, Albuquerque, N. Mex., an 8 mm diameter rotary piezo motor. Early evaluation of this 8 mm motor showed that the drive frequency required to operate the motor at its highest output torque and speed is the most critical variable associated with its operation. Experimental evaluation showed that many other variables also effect the operating frequency. Most importantly for many applications, temperature has the largest effect on the operating frequency. Since the operating frequency shifts as a function of temperature, the drive electronics design must be able to shift the drive frequency to maintain optimum performance from the motor.